my phone shut off in the middle, and it said that it failed. Now I'm back to the "firmware upgrade encountered an issue, please connect to kies and try again" screen. I can still get into download mode. What now?
It apparently tripped my warranty bit too
and it shuts off within 3 seconds when on download mode. I read something about "sudden death syndrome". Is this it?

Start from something very simple. Check if your power button is not stack or push in all the time. I fixed mine by removing battery and i put drop of vegetable oil in power button, maybe not drop just little and i push button couple times.

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